1. Field of the Invention
This invention relates to a keyboard switch information assignor which is adaptable to a variety of specifications in electronic keyboard instruments of the digital processing type tone generation system.
2. Description of the Prior Art
In electronic keyboard instruments of the digital processing type tone generation system, the provision of tone generating means respectively corresponding to keyboard switches, as is usually seen in the analog processing type tone generation system, merely introduces complexity in the system arrangement to make it far from practical use. For the solution of this problem, it is customary in the prior art to restrict the number of sounds to be produced simultaneously to such an extent as not to impose limitations on the player; namely, the system employed therefor is such that key switch information is stored by an assignor in assignment memories provided respectively corresponding to tone generating means of the same number as the sounds to be produced simultaneously and is selectively read from the memories to obtain desired musical sounds. In the practical application of such an assignor, it is desirable that the assignor is fabricated as an integrated circuit instead of a mere assembly of a number of individual parts and can be used in common to a wide variety of electronic keyboard instruments so as to reduce the manufacturing cost of the integrated circuit by mass production.
Generally, in the electronic keyboard instrument, the numbers of key switches and keyboards used both vary with the scale of the instrument, namely, the numbers of key switches adopted at present at 61, 49, 44, 37, 25 and 13, and the number of keyboards ranges from 1 to 3 or more. The common use of the same assignor in such various keyboard instruments is advantageous economically but introduces much redundancy in their arrangements. Further, there is a large difference in the playing ability between players of large- and small-scale keyboard instruments, and it is desirable to set a limit to the number of sounds to be produced simultaneously in consideration of such difference; this is also an obstacle to the application of the same assignor in common to different types of electronic keyboard instruments.
Moreover, since the algorithm of the assignor has not as yet been established, a particular assignor may sometimes impose an unexpected limitation on the player and, in such a case, the method of assignment is obliged to be modified; therefore, it might be said that the fabrication of the assignor as an integrated circuit is in constant danger of total abandonment. Accordingly, it is desired to obtain an assignor capable of easy modification of its specification.